Resinous coatings adapted to receive a light-sensitive layer in the production of lithographic printing plates



RESINOUS COATINGS ADAPTED TO RECEIVE A LIGHT-SENSITIVE LAYER IN THE PRODUCTION OF LITHOGRAPHIC PRINTING PLATES Elmer F. Deal, West Covina, Isadore M. Richlin, San

Gabriel, and Bruce W. Wilson, Pomona, Calif., assignors to Lithoplate, Inc., a corporation of California No Drawing. Filed Dec. 21, 1962, Ser. No. 246,314

10 Claims. (Cl. 117-62.2)

This invention relates to a lithographic plate base adapted to receive a light sensitive coating to provide a sensitized lithographic plate and to methods of preparing such a base.

This application is a continuation-in-part of our copending application Serial No. 765,043, filed October 3, 1958, now Patent 3,073,723, dated January 15, 1963, which contains the generic claims to inventions described and claimed herein.

One of the features of this invention is to provide an improved lithographic plate base adapted to receive a light sensitive coating comprising a base member, and a coating thereon formed by applying to the base (1) a water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine -resins, and melamine-formaldehydepolyalkylenepolyamine resins, (2) a water soluble carbon atoms chain polymer to which atoms are attached -COR radicals in which R is a group of the class consisting of OH, NH -OCH and -OC H with about 100% of said radicals being COOH and with adjacent radicals being separated by not more than three of said carbon atoms, and (3) as a curing agent, a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of Zirconium, hafnium, titanium and thorium and said coating being substantially free of unreacted salts of said metal.

A further feature of the invention is to provide a method of making such a plate base comprising applying to a base member an aqueous dispersion of (1) a water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-formaldehyde-polyalkylenepolyamine resins at a concentration of about 0.1- 2.0%, and an aqueous dispersion of (2) a water soluble carbon atoms chain polymer to which atoms are attached COR radicals in which R is a group of the class consisting of OH, NH -OCH and --OC H with about 10100% of said radicals being COOH and with adjacent radicals being separated by not more than three of said carbon atoms at a concentration of about 0.001- 10.0%, and (3) as a curing agent, an aqueous solution of a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal, the salt being at a concentration of about 0.01-10.0%, all said amounts being by weight, and washing said thusly coated base member with Water.

The lithographic plate base of this invention permits 3,232,783 Patented Feb. 1, 1966 the use of any base member desired such as metal sheet or foil, glass, synthetic plastic, wood, paper or other such material that is dimensionally and chemically stable. The reason for this is that the adherent barrier layer which is applied to at least one surface of the base member does not appear to react chemically with the base member but merely to bond intimately thereto. Of the metals a preferred base member is either copper, tin, aluminum, manganese, zinc or chromium, although others may of course be used if desired. A preferred aluminum base member is one described in Wood Patent 2,240,732 which is primarily aluminum containing about 1.25% manganese.

The lithographic plate has adhered to this base member a novel adherent barrier coating which seals the surface of the base member and particularly the metal base member in that there is no contact between the base member and a subsequently applied overlying light sensitive coating or sensitizer. As a result a presensitized plate of this invention has good shelf life and can be stored for long periods of time. In addition the barrier layer is hydrophilic and oleophobic so as to be scum preventing and to reduce tone in the resulting printing plate. Also, it is substantially free of water soluble material. A combination of this barrier layer and the subsequently applied sensitizer also produces extremely long runs of operation so that the printing plate may be used to make several thousand impressions.

The barrier layer is produced in a series of steps. In one step the base member has applied thereto an aqueous dispersion of a modified aldehyde condensation product. This resin may be any of four different types or a mixture of these. One such resin is an alkylated (methylated or ethylated) methylol melamine resin produced as described in the US. Patent No. 2,715,619. The disclosure of this reference is incorporated herein by reference. In general, the process described in this patent comprises the following steps: (A) reaction of melamine with formaldehyde in a mixture containing controlled amounts of etherifying alcohol and water under alkaline conditions, (B) alkylation under acid conditions, with additional alcohol, if necessary, and (C) concentration of the neutralized syrup to remove the excess and unreacted alcohol.

Another resin that may be used on the base member is a polyalkylenepolyamine melamine formaldehyde resin produced as disclosed in US. Patent 2,796,362. The disclosure of this patent is also included herein by reference. The resins useful herein are characterized by content of at least five and preferably more than six mols of combined formaldehyde per mol of melamine with the number of nitrogen atoms in the polyalkylenepolyamine per mol of melamine being between 0.5 and 10.0 and the resin being cationic.

Another aldehyde resin that may be used in this process is the amine modified urea-formaldehyde resin disclosed in US. Patent 2,554,475. The disclosure of this patent is also included herein by reference.

These resins are infinitely water-dilutable polyfunctional compounds in which the polyfunctional amine contains at least two functional amino groups and are prepared generally by reacting a polyfunctional amine or salt thereof with urea and formaldehyde or with the condensation product of urea and formaldehyde at a pH and temperature such that there is no viscosity increase, followed by aging at a pH and temperature such that the viscosity increases steadily at a controllable rate.

In a preferred process the urea and an aqueous solution of formaldehyde is reacted at from about 70-80 C. for about 15-30 minutes under alkaline conditions with the mol ratio of urea to formaldehyde being between 1:f2-1:2 .8 followed by adding thereto about 2-8% of a polyfunctional amine based on the weight of urea, adjusting the pH to between 1 and 4 and reacting by heating at a temperature of from about 68 C. to reflux temperature for about 15-180 minutes followed by reducing the temperature to one between about room tem perature and 55 C.

Another resin that may be used is an alkali metal sul-furous acid salt modified urea-formaldehyde resin produced as described in US. Patent 2,559,578 which disclosure is included herein by reference.

The resin is preferably applied to the clean base member in an aqueous dispersion and then the excess is rinsed off after a preferably relatively short interval of time with running water which may be tap water. In the preferred process the resin is employed in an aqueous dispersion containing about 0.1 to 20.0% of resin by weight and the base member is treated with this solution for a brief time, preferably from about 10 seconds to 5 minutes. The temperature of the dispersion is lower than the boiling point of water and for commercially satisfactory reasons is preferably from about room temperature to 185 F.

After application of the resin dispersion to the base member it is rinsed with water, preferably running water, which may be tap water.

As set out above, the base member may be any dimensionally stable material and may include a base member made up of two or more layers. Thus it may be a paper sheet or plate impregnated with a resin such as a thermosetting resin like phenol or urea-formaldehyde and the preferred resin either when used alone or in conjunction with a baking is a heat resistant thermoset resin. The term base member as used herein therefore includes sheet, film, foil, plate or other stable body. After the resin treated base member as set out above has been washed, as specified, it is coated with an aqueous dispersion of a water soluble carbon atoms chain polymer to which atoms are attached -COR radicals in which R is a group of the class consisting of OH, -NH OCH and OC H with about -100% of said radicals being -COOH and with adjacent radicals being separated by not more than three of said carbon atoms.

The water soluble polymer made up of carbon atom chains or chain having the above-described substituents on certain carbon atoms may be either straight chain or cross-linked. The polymers must be either completely water soluble or water dispersible in molecular units in order to be usable.

The molecular weight of these polymers is preferably at least 50,000 with a practical upper limit being 1,000,000. In certain instances, however, polymers as low as 10,000 molecular weight may be used, and the only upper limit on the molecular weight is the practical one of ease of dispersion or solution in water and the viscosity resulting therefrom. The more viscous the water solutions, the greater the time required to produce the bases of this invention.

The above polymeric coating material is preferably applied in aqueous dispersion of a concentration of about 0.01-10.0% of the material in Water and at a preferred temperature between room temperature and 185 F. The application of the water dispersion compound may be as rapidly as practicable with a time between 5 seconds and 10 minutes being found most desirable for common commercial practice. As soon as the aqueous dispersion has been applied the plate is again rinsed with water that may be tap water.

Polymers useful in this invention are the water-soluble and water-dispersible members of the following groups: (1) the homologous polyacrylic acids; (2) the materials of (1) in which up to of the carboxylic acid groups have been converted to carboxarnides; (3) polycarboxylic acids formed by the hydrolysis of the copolymers formed by maleic anhydride and ethylene, styrene, vinyl methyl ether, or vinyl acetate; (4) the mixed carboxylic acid-carboxamides formed by the ammonalysis of the copolymers in (3) above; and (5) the mixed carboxylic acid-esters formed by the alcoholysis of the copolymers of (3) above with either ethanol or methanol.

Typical polymers that are usable in this invention include the following:

Polyacrylic acid.

Polymethacrylic acid.

Copolymer of acrylic acid and methacrylic acid.

Acrylic acid-acrylamide copolymers wherein the ratio may vary from 90:10 to 10:90.

Hydrolyzed polyacrylamide wherein the ratio may run only from 10-70% carboxy to 90-30% carboxamide.

Hydrolyzed polyacrylonitrile having a ratio of about 10-70% carboxy to 90-30% carboxonitrile.

Methacrylic acid-acrylamide copolymer, with ratios of monomers from 90:10 to 10:90.

Hydrolyzed polymethacrylamide with ratios of 10-70% carboxy to 9030% carboxamide.

Hydrolyzed styrene-maleic anhydride copolymer wherein from about 30-100% of the anhydride groups have been converted to dicarboxy groups.

Hydrolyzed ethylene-maleic anhydride copolymer with the requirements as above.

Hydrolyzed vinyl methyl ether-malei-c anhydride copolymer with the requirements as above.

Hydrolyzcd acrylonitrile-maleic anhydride copolymer with the requirements as above.

Hydrolyzed vinyl acetate-maleic anhydride copolymer with the requirements as above.

Derivatives prepared as in the next preceding 5 examples but ammonolyzed to completion instead of hydrolyzed.

Derivatives as presented in the next preceding example except alcoholyzed to completion instead of hydrolyzed.

As soon as the base member containing the first above defined coating is coated with the second coating it is contacted with a third material which is an aqueous solution of a water soluble compound of a metal which is either zirconium, hafnium, titanium or thorium, with zirconium and hafnium being preferred. The metal compound is preferably a salt with the acid radical of the salt being any that will make the compound water soluble and that will not react with the base member of the previously applied coating thereon or with the subsequently applied sensitizer or light sensitive material. Typical salt groups are the acetates, nitrates and sulfates and these are relatively inexpensive and easy to obtain. Other salts may be used of course subject to the foregoing qualifications. The metal compound solution preferably has a concentration of 0.01-10.0% by Weight and is preferably applied at a temperature of from room temperature to about F. In each of the treating baths the upper limit of 185 F. is merely a practical upper limit as any temperature may be used below the boiling point of water. The treatment with the metal salt solution may be as rapidly as practical and in com-- mercial instances has been found to be between 5 sec-- onds and 10 minutes.

After application of the metal salt solution the plate is again rinsed off with water, preferably running water such as tap water. The resulting lithographic plate base may be stored as such and used later by application of the sensitizer as, for instance, it may be shipped to a user and the user himself may apply the sensitizer. If desired, the sensitizer is applied by the manll ifiqturer to produce a presensitized lithographic plate and the resulting plate may be stored in the dark for weeks and even months such as in a light proof storage package. The presensitized plate may then be used in the customary manner by exposing the light sensitive coating to a source of light such as ultraviolet light through a negative or the like, as previously described followed by washing oil the unreacted sensitizer and further treatment as is customary in this art before being used to produce printing sheets or the like.

The light-sensitive material that is applied to the thusly produced plate base may be of any of the usual watersoluble or water-dispersible lithographic sensitizers including, but not limited to, bichromated natural colloids such as casein, albumin, gum arabic, gelatin, and glue;

'bichromated synthetic colloids such as partially or completely hydrolyzed polyvinyl acetate and polyvinyl pyrrolidone, bichromated shellac, various silver or iron sensitized emulsions; and certain diazonium salts, either alone or in combination with colloids.

The exposed light sensitive material thus provides a printing image while the material itself being water soluble can be washed away from the unexposed areas leaving the above described underlying hydrophilic surface tree of the sensitizer. As is well known in this artthe albumin sensitizer may be prepared by applying .to the base a water solution of albumin that has previously been made sensitive to the action of light bythe addition of a sensitizing agent such as ammonium chromate or dichromate. After the solution has been applied the plate is permitted to dry .and is then ready to be exposed to light. Other such sensitized dispersions or solutions include halogenated polyvinyl alcohol in aqueous dispersion or solution as described in Patents 2,179,245, 2,199,865 and 2,342,175 or dispersions or solutions of proteins such as casein described in Patents 2,324,197, 2,324,198 and 2,500,453.

It will be noted that, while most of the sensitizers named yield negative-working so-called surface plates,

a number of the sensitizers may be used in the positiveworking deep-etch system. Such bichromated colloids as gum arabic and glue, for example, yield on exposure and development strong but temporary stencils suitable for the deep-etch process.

Typical diazo sensitizers are ideally suited for use with the prepared base of this invention and typical sensitizers of this type are described in Patents 2,100,063, 2,667,415, 2,679,498 and 2,772,972. Such a diazo compound is prepared by condensing paraformaldehyde with p-diazo-diphenylamine sulfate. The aqueous dispersion or solution of the sensitizer or light sensitive material may be applied to the prepared base by dipping, spraying, roller coating, brushing or the like which are all conventional in this art.

When a metal plate such as an aluminum plate is used as the base member the plate is preferably oxidized although the unoxidized surface may be used if desired. This oxidizing of aluminum, for example, is accomplished in the customary and well known manner either by using an oxidizing agent or electrolytically. One way of oxidizing aluminum is by applying thereto a 2% solution of chromic acid in water at 150 F. This is a well known and customary oxidizing method.

Wherever the terms soluble and water dispersible are used herein they are intended to include both water soluble and molecular and multimolecular dispersions as well as those dispersions that are dilutable with water.

The metal compounds used in this invention appear to act as agents in curing the two previously applied coatings. Although the exact nature of the action has not been proven chemically it appears that all of the three coatings interact to form a single layer that is adherent to both the base member and to the light exposed sensitizer.

6 The following examples are illustrative only of the many methods of preparing the base plate of this invention.

Example 1 A thin sheet of aluminum was etched and cleaned by washing for three minutes at F. in a 10% aqueous solution of anhydrous trisodium phosphate. The thusly treated aluminum sheet was then rinsed with a spray of tap water for three minutes. It was then desmutted by immersion in a bath of 2% chromic acid and .8% sulfuric acid in water for three minutes at room temperature. At the end of this time the sheet was rinsed for three minutes in a spray of tap water. The sheet was then immersed for two minutes in a 3% aqueous dispersion of resin prepared as described in Patent 2,796,362. The plate was again rinsed in tap water. The plate was then immersed for about 5 seconds in a 0.001% solution of polyacrylic acid having a molecular weight of about 50,000 and a pH of about 3. After withdrawing the plate was rinsed with a tap water spray. The plate was then immersed in a 1% aqueous solution of zirconium acetate salt and the treated sheet was then again rinsed in tap water and dried. The thusly treated sheet was then ready for a coating of sensitizer.

In this example the sensitizer was a customary aqueous dispersion of bichromated casein of the type described in Patent 2,324,197.

Example 2 Thesame procedure as in Example 1 was followed except here the polymer was polymethacrylic acid with a molecular weight of 100,000.

Example 3 This example was the same as Example 1 except the polymer was hydrolyzed polyacrylonitrile of a molecular weight of about 75,000 containing about 70% COOH and 30% CONH at a concentration in the solution of about 0.01% and in this example, as in each of Examples 1 and 2, the solution was at room temperature. The polymer of this example was in the form of the commercial sodium salt at a pH about 6.8.

Example 4 This example is the same as Example 1 except that the polymer is an acrylic acid-acrylamide copolymer having a molecular weight of about 1,000,000 and containing 30% carboxy groups to 70% carboxamide groups and is the free acid. The concentration in the aqueous solution was 0.01% and the solution was at room temperature and had a pH of about 3.

Example 5 In this example the polymer was a completely hydrolyzed styrene-maleic anhydride polymer in the form of the sodium salt and was used in an aqueous solution at a concentration of about 0.1%, a pH of about 7.0 and a temperature of about 70 C.

Example 6 This example was the same as Example 5 except that the free acid was used and the solution had a pH of about 3.

Example 7 This example was the same as Example 6 except the copolymer was the ethylene-maleic anhydride copolymer with all other conditions being the same.

Example 8 This example was the same as Example 1 except the polymer was hydrolyzed polyacrylamide of a molecular weight of about 300,000 and a 10:90 proportion of carboxy to carboxamide groups. The sodium salt of the amide was used at a concentration in water of about 0.1%.

The solution had a pH of about 7.5 and was at a temperature of about 70 C.

Example 9 This example was the same as Example 7 except that the polymer was in the form of the free acid and the solution had a pH of about 3.

Example 10 This example was the same as Example except that the polymer was hydrolyzed vinyl methyl ether-maleic anhydride.

Example 11 This example was the same as Example 5' except that the hydrolysis was only carried out on approximately one-half of the anhydride bonds.

Having described our invention as related to the embodiments set out herein, it is our intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

All parts and percentages given herein are by weight.

We claim:

1. A plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: a base member; and a coating thereon formed by applying to the base member (1) a Water dispersible resin of the class consisting of amine modified urea-formaldehyde resins, alkali metal snlfurous acid salt modified urea-formaldehyde resins, alkylated methylol mela mine resins, and melamine formaldehyde-polyalkylenepolyamine resins, (2) a water soluble polyacrylic acid, and (3) as a curing agent, a Water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal.

2. A plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: a base member; and a coating thereon formed by applying to the base member (1) a water dispersible resin of the class consisting of amine modified ureaformaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-forrnaldehyde-polyalkylenepolyamine resins, (2) a water soluble carbon atoms chain polymer to which atoms are attached COR radicals in which about 90l0% of said COR radicals are COOH and about -90% of said COR radicals are CONH and with adjacent radicals being separated by not more than three of said carbon atoms, and (3) as a curing agent, a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal.

3. A plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: a base member; and a coating thereon formed by applying to the base member (1) a water dispersible resin of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-formaldehyde-polyalkylenepolyamine resins, (2) a water soluble ammonolyzed maleic anhydride copolymer in which 30-100% of the original acid anhydride groups have been converted to equivalent numbers of carboxy and carboxa-mide groups, and (3) as a curing agent, a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal.

4. A plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: a base member; and a coating thereon formed by applying to the base member (1) a water dispersible resin of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified ureaformaldehyde resins, alkylated methylol melamine resins, and melamine formaldehyde polyalkylenepolyamine resins, (2) a water soluble maleic anhydride copolymer in which 30100% of the original acid anhydride groups have been alcoholyzed by an alcohol containing no more than two carbon atoms to produce equivalent numbers of carboxy groups and ester groups corresponding to the alcohol employed, and (3) as a curing agent, a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal.

5. A plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: a base member; and a coating thereon formed by applying to the base member (1) a water dispersible resin of the class consisting of :amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-f0rmaldehyde-polyalkylenepolyamine resins, (2) a water soluble hydrolyzed maleic anhydride copolymer in which from about 30-lO0% of the anhydride groups have been converted by the hydrolysis to dicarboxy groups, and (3) as a curing agent, a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that cat a metal of the class consisting of zirconium, hafniulm, titanium and thorium, said coating being substantially free of unreacted salts of said metal.

6. The method of making a plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: forming a coating by applying to a base member an aqueous dispersion of (l) a water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal suifurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamineformaldehyde-polyalkylenepolyamine resins at a concentration of about 0.2-2.0%, an aqueous dispersion of (2) a Water soluble polyacrylic acid at a concentration of about 0.001l0.0% and (3) as a curing agent, an aqueous solution of a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, ih'afnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal, the salt being at a concentration of about OBI-10.0%, all said amounts being by weight; and washing said thusly coated base member with water.

7. The method of making a plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: forming a coating by applying to a base member an aqueous dispersion of (l) a water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamineformaldehydc-polyalkylenepolyamine resins at a concentration of about O.l-2.0%, an aqueous dispersion of (2) a water soluble carbon atoms chain polymer to which atoms are attached COR radicals in which about l0% of said COR radicals are COOH and about 10-90% of said COR radicals are CONH and with adjacent radicals being separated by not more than three of said carbon atoms and at a concentration of about 0.001 10.0%, and (3) as a curing agent, an aqueous solution of a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal, the salt being at a concentration of about OBI-10.0%, all said amounts being by weight; and Washing said thusly coated base member with water.

8. The method of making a plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: forming a coating by applying to a base member an aqueous dispersion of (l) a water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-formaldehydepolyalkylenepolyamine resins at a concentration of about 0.12.0%, an aqueous dispersion of (2) a water soluble ammonolyzed maleic'anhydride copolymer in which 30- 100% of the original acid anhydride groups have been converted to equivalent numbers of carboxy and carboxamide groups and at a concentration of about 0.001- 100%, and (3) as a curing agent, an aqueous solution of a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal, the salt being at a concentration of about 0.0l-10.0%, all said amounts being by weight; and washing said thusly coated base member with water.

9. The method of making a plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: forming a coating by applying to a base member an aqueous dispersion of (1) a Water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal s-ulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-formaldehydepolyalkylenepolyamine resins at a concentration of about 0.1-2.0%, an aqueous dispersion of (2) a Water soluble maleic anhydride copolymer in which 30-100% of the original acid anhydride groups have been alcoholyzed by an alcohol containing no more than two carbon atoms to produce equivalent numbers of carboxy groups and ester groups corresponding to the alcohol employed and at a concentration of about 0.00l10.0%, and (3) as a curing agent, an aqueous solution of a water soluble salt alone and prior to the application of said light sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal, the salt being at a concentration of about 0.01- 10.0%, all said amounts being by weight; and washing said thusly coated base member with Water.

10. The method of making a plate base adapted to receive a light sensitive layer to provide a presensitized lithographic plate, comprising: forming a coating by applying to a base member an aqueous dispersion of ('1) a water dispersible member of the class consisting of amine modified urea-formaldehyde resins, alkali metal sulfurous acid salt modified urea-formaldehyde resins, alkylated methylol melamine resins, and melamine-formaldehydepolyalkylenepolyamine resins at a concentration of about 0,l2.0%, an aqueous dispersion of (2) a water soluble hydrolyzed maleic anhydride copolymer in which from about 30-100% of the anhydride groups have been converted by hydrolysis to dicarboxy groups and at a concentration of about 0.00l10.0%, and (3) as a curing agent, an aqueous solution of a water soluble salt alone and prior to the application of said light. sensitive layer, said salt being that of a metal of the class consisting of zirconium, hafnium, titanium and thorium, said coating being substantially free of unreacted salts of said metal, the salt being at a concentration of about 0.0110.0%, all said amounts being by weight; and washing said thusly coated base member with Water.

References Cited by the Examiner UNITED STATES PATENTS 8/1956 Beatty 9633 1/1963 Deal et a1. 1l7-161 

1. A PLATE BASE ADAPTED TO RECEIVE A LIGHT SENSITIVE LAYER TO PROVIDE A PRESENSITIZED LITHOGRAPHIC PLATE, COMPRISING: A BASE MEMBER; AND A COATING THERON FORMED BY APPLYHING TO THE BASE MEMBER (1) A WATER DISPERSIBLE RESIN OF THE CLASS CONSISTING OF AMINE MODIFIED UREA-FORMALDEHYDE RESINS, ALKALI METAL SULFUROUS ACID SALT MODIFIED UREA-FORMALDEHYDE RESINS, ALKYLATED METHYLOL MELAMINE RESINS, AND MELAMINE FORMALDEHYDE-POLYALKYLENEPOLYAMINE RESINS, (2) A WATER SOLUBLE POLYACRYLIC ACID, AND (3) AS A CURING AGENT, A WATER SOLUBLE SALT ALONE AND PROIR TO THE APPLICATION OF SAID LIGHT SENSITIVE LAYER, SAID SALT BEING THAT OF A METAL OF THE CLASS CONSISTING OF ZIRCONIUM, HAFNIUM, TITANIUM AND THORIUM, SAID COATING BEING SUBSTANTIALLY FREE OF UNREACTED SALTS OF SAID METAL. 